Since the genesis of the integrated circuit, various types of devices have evolved. Such devices typically include DIP's (dual in-line packages), SOIC's (small outline integrated circuits), PLCC's (plastic leadless chip carriers), etc. Such devices have innumerable applications in industry and commerce.
With many of the applications to which such devices can be put, it is essential that the devices be accurate to at least a minimum defined percentage of accuracy. In some applications, of course, it is essential that the devices be virtually one hundred percent accurate. In other applications, however, a reliability, for example, of eighty percent might be acceptable if certain critical circuit paths are completely accurate.
The manufacturing processes employed in creating integrating circuits do, as in the case of other manufacturing processes, produce units of different quality. For this reason, it is necessary to test the items (that is, effect quality control). Such testing is performed not only to answer the question of whether or not the devices are merely operable to any degree, but also to classify the units by degree of operability.
Various testing devices have been developed in order to perform such quality control operations. Typically, such testers perform testing at high rates of speed. Handling devices have also been developed which, it is intended, are capable of feeding integrated circuits to a test site interfacing with the tester. Such handler equipment should, of course, feed the devices to the test site rapidly, and they should also convey the devices to be tested away from the test site at a high rate of speed.
A number of high-speed handlers have been developed to achieve these goals. In order to facility ever increasing speed requirements, multiple test site handlers have been designed.
Depending upon the type and nature of the device and the application in which the device is to be used, an integrated circuit will be subjected to different ambient operating temperatures. In one application, a device to be tested might ultimately function in an environment with a temperature significantly higher than room temperature. On the other hand, however, another device might ultimately be intended to function in an environment with a temperature significantly lower than ambient temperature.
A particularly important feature of a handler is one whereby an input tray of the handler is brought to a temperature so that integrated circuits fed therethrough are elevated or depressed to the temperature of the environment in which the devices are intended to ultimately operate. One manner in which the prior art has attempted to accomplish this goal is by providing an input tray which functions as a temperature chamber. The temperature in the chamber can be elevated or lowered by introducing a gas to the effects of which the integrated circuit devices are subjected as they pass through the chamber defining the tray. An appropriate gas is injected into the chamber to lower the temperature below a desired set point. The gas, itself, has no function in actually adjusting the temperature. Electrical heaters, however, are provided to heat the integrated circuits on the tracks within the chamber. Since the initial temperature achieved by the gas is below the desired temperature, the heaters raise, and discriminately adjust, the temperature to the desired level.
Regardless of the method of achieving a desired temperature, however, it is important that the temperature sought to be achieved be, in fact, within a close tolerance range. It is important that an operator of the machine be able to rely upon the machine being properly calibrated for temperature so that the integrated circuit devices will be able to be determined to have been accurately tested. Testing under the proper temperature conditions is, of course, a significant factor in this reliance.
In the prior art, calibration of a handler has been a long drawn-out and tedious process. Heretofore, intervention of the machine's operator has been necessary at various stages of the calibration evolution. As a result, it is not uncommon for the full temperature calibration process to take up to four to eight hours. As can be seen, a significant block of man hours is consumed in effecting calibration. Certainly, time could be better utilized if the process took less time.
It is to these problems and dictates of the prior art that the present invention is directed. The present invention is an improved apparatus and method for effecting temperature calibration of an integrated circuit handler which feeds devices to be tested to a test site which interfaces with an IC tester.